Press tool comprising a spindle for moulding coupling elements

ABSTRACT

The aim of the invention is to configure an electrically driven press tool in as compact, reliable and cost-effective a manner as possible. To achieve this, the invention provides a press tool, in which a crimping tool ( 43 ) is retained in a recess ( 3 ) by a bolt ( 5 ). An electromotor ( 10 ) drives a spindle ( 14 ), which interacts with the crimping tool ( 4 ), by means of a reducing gear ( 11 ). C The spindle ( 14 ) is connected to a shaft ( 13 ) by means of a pressure flange ( 17 ). The bearing pressure, which acts on the spindle ( 143 ), is brought to bear on a pressure ring ( 27 ) by means of a pressure flange ( 17 ) and a pressure bearing ( 18 ), said ring acting directly or indirectly on a force or pressure sensor ( 25 ). When a predetermined set value of the crimping force has been reached, the sensor.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electrically operated pressing tool for connecting tubular workpieces, with a fork-like receiver, with a clamping pincer exchangeably held in this receiver by way of a connection bolt, and with a controlled electric drive motor for actuating the clamping pincer, wherein there is present a spindle which is driven by an electric drive motor via a reduction gear and which is in active connection with the clamping pincer.

[0002] Portable, electrically functioning pressing tools of the initially mentioned type are used for pressing coupling elements such as press sleeves, press fittings, connecting sleeves, tube sections inserted into one another and likewise. The pressing tools comprise a clamping pincer with clamping jaws which form a pressing space for receiving the coupling element to be pressed. The pressing pressure required for the pressing was initially produced by an electric motor connected to the mains, via a forward and rearward running spindle which acts on a joke provided with two rollers, wherein the rollers move the clamping jaws of the clamping pincer.

[0003] These pressing tools have proven themselves and are extremely widespread. In the course of development one has moved more and more from spindle-operated versions and one has used hydraulically operated pressing tools. With these hydraulically functioning tools as previously one operates with an electromotoric drive which however now actuates a pump by way of which a piston is displaced whose piston rod acts on the yoke in which the two mentioned rollers are mounted. These hydraulically operated pressing tools may be controlled extraordinarily exactly by way of a combined monitoring of the hydraulic pressure to be built up as well as the monitoring of the path which checks the exact closure of the clamping pincer

[0004] A further advantage of the hydraulically functioning pressing tools is to be seen in the fact that battery-operated electric motors may also be applied, by which means one may operate independently of the mains. Thanks to the hydraulic drive one may also apply battery-operated electric motors which initially still had a relatively low torque.

[0005] For all previously mentioned pressing tools one applied different clamping pincers corresponding to the large number of different coupling elements for a large range of the most varied of diameters. The diameters of common coupling elements lie in the region of 10 to more than 100 mm. The most common range of application however lies between 10 and 30 mm. Despite this practically all pressing tools offered on the market today are designed for the complete application range. Accordingly the pressing tools known today are relatively large and accordingly heavy. Although there exists a corresponding demand for portable, smaller and lighter pressing tools for the most common range between for example 10 and 50 mm diameter of the coupling elements, such apparatus however are not obtainable on the market until today. An essential reason for this above all lies in the safety and monitoring of the pressure which is built up by the pressing tools. The arising pressures which are to built up with hydraulic systems necessitate a correspondingly heavy and safe design of the pressing tool and a corresponding reduction which regard to scale is not possible without completely different clamping pincers being used. In order to obtain the required safety with spindle-operated pressing tools, accordingly between the electric motor and the spindle there has been arranged a clutch in front of or after the gear for reasons of safety. This has made the spindle-operated apparatus as a whole heavier, more expensive and larger. Various suppliers have brought apparatus of the type described here onto the market.

[0006] From U.S. Pat. No. 6,035,775 there is known a pressing tool functioning with a spindle, with which the pressure to be built up is electronically monitored in that the rotation speed of the electric motor is monitored and is led and controlled with a predefined profile within a certain bandwidth. These characteristics of pressing are essentially dependent on the size, shape and nature of the material of the coupling elements and thus permit the provision of a pressing procedure which is carried out in a pressure-dependent and time-dependent manner.

BRIEF SUMMARY OF THE INVENTION

[0007] It is the object of the present invention to modify the design of a pressing tool in a manner such that this may be constructed smaller, less expensively and lighter without at the same time losing safety aspects.

[0008] A pressing tool of the previously mentioned type with the features of patent claim 1 achieves this object.

[0009] Advantageous embodiment forms result from the dependent claims and their significance and manner of acting is described in the subsequent description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings shown simplified is a preferred embodiment form. There are shown in

[0011]FIG. 1 a possible embodiment form of the pressing tool in a total view, in a perspective representation.

[0012]FIG. 2 shows an axial longitudinal section through the spindle drive in a simplified representation.

DETAILED DESCRIPTION OF THE INVENTION

[0013] The pressing tool 0 is an electromechanical apparatus which here is realized as a battery-operated apparatus. The pressing tool 0 has a pressing tool function unit 2 on which a grip 1 is integrally formed. In the rearward extension a battery housing 6 is integrally formed on the function unit 2 as a removable part. In the forward extension of the pressing tool function unit 2 one may recognize a fork-like receiver 3. A clamping pincer 4 is held in the fork-like receiver 3. This is securely held in the receiver 3 by way of a monitored safety bolt 5. A trigger switch 8 as is usual is present for actuating the apparatus. The functional condition of the pressing tool is displayed on a display unit 7, whilst the user is informed by way of light diodes whether a pressing could be carried out correctly or not.

[0014] The construction of the function unit 2 may be deduced in detail from FIG. 2. Here from the left to the right in the drawing one may clearly recognize the electric drive motor 10 which acts on a shaft 13 via a reduction gear 11 and its drive pinion 12. The shaft 13 drives a threaded spindle 14 on which a spindle nut 16 runs and displaces a roller advance element 15 which is translatorily moved into the fork-like receiver 3.

[0015] The electric motor 10 may be designed infinitely as a d.c. or a.c. motor. One would most preferably select an electric motor with a lower mass and a high torque. Such motors are obtainable on the market in the most varied of embodiment forms. The output drive of the electric motor 10 is effected onto a reduction gear 11. With this it is the case of a completely traditional gear which is connected to a shaft 13 via a drive pinion 12. The connection between the drive pinion 12 and the shaft 13 may be realized as a simple, practically play-free plug connection. The shaft 13 is preferably manufactured as one piece and axially flush with the threaded spindle 14. The threaded spindle 14 is provided with a trapezoid thread suitable for transmitting large forces. In contrast to pressing tools known on the market, thus here one does not operate with ball-bearing spindles, but as mentioned with a simple and accordingly inexpensive threaded spindle 14. A spindle nut 16 which is seated on the threaded spindle 14 runs forwards or backwards on the spindle 14 according to the drive. This threaded spindle 16 is rigidly connected to a roller advance element 15. The roller advance element 15 at the same time is the spindle and a part of the shaft 13 is mounted in a spindle housing 21. To this spindle housing 21 there connects the fork-like receiver 3 into which the roller advance element 15 advancingly and retreatingly moves. The roller advance element 15 is passed through by axis pins 31 on which rollers 30 are mounted, which cooperate with clamping jaws 40 of the clamping pincer 4 and accordingly closes the clamping pincer 4.

[0016] Whilst the spindle housing 21 which forms part of the housing of the function unit 2 in the direction of the clamping pincer 4 is limited by the fork-like receiver 3, on the motor side the spindle housing 21 is closed off by a housing plate 20. The shaft 13 passes through this housing plate 20 and is mounted in the housing plate 20 itself in a radial bearing 19. The shaft 13 is limited towards the spindle 14 by a pressure flange 17. Between this pressure flange 17 and the housing plate 20 lies an axial thrust bearing 18, a thrust ring 27 which acts directly or indirectly onto a force sensor or pressure sensor 25. With regard to design, this may be effected most simply with annular force or pressure sensors present on the market which one would arrange between the thrust ring 27 and the housing plate 20. Such force or pressure sensors however are today still quite expensive and accordingly a solution is shown here in which one may operate with a small and extremely inexpensive piezoelectric force and pressure sensor 25. However indeed a design adaptation might be considered which would use a wire strain gauge as a force sensor. For this a lever 26 and a counter-pressure ring 28 are provided between the thrust ring 27 and the housing plate 20. The relative position of the lever 26, of the thrust ring 27 as well as the counter-pressure ring 28 is rotationally secured by way of a pin 29, wherein the pin 29 engages into the housing plate 20. Balls 24 are applied between the counter-pressure ring 28 and the lever 26 on the one side and between the lever 26 and the thrust rung 27 on the other side, and these balls permit a pivot movement of the lever 26.

[0017] If a user actuates the trigger switch 8, then the electric motor 10 via the reduction gear 11 drives the shaft 11 and the threaded spindle 14, by which means the spindle nut 16 slides forwards in the direction of the fork-like receiver and thus the roller advance element with the rollers 30 is moved to the right in the figure. The rollers 30 run on the cheeks of the clamping jaw 40 of the clamping pincer 4 and close this. The reaction force leads to an increased pressure of the spindle 14 and thus of the pressure flange 17 connected thereto onto the thrust bearing 18 which transfers this pressure further onto the thrust ring 27. The whole pressure is finally led onto the rigid housing plate 20. As already mentioned either the reaction force of the ring 27 is led directly onto a force or pressure sensor 25, or, as shown here the pressure is effected via the lever system with the balls 24, wherein the lever 26 carries out a slight pivot movement or a slight deformation which leads to a pressure on the force or pressure sensor 25. If this pressure reaches a predefined limit value, then a signal S is released by the force or pressure sensor 25 to a control 22 and the control 22 leads to a reversing of the electric motor 10 which now rotates in the counter direction. As a consequence of this the threaded spindle 14 runs in the reverse rotational direction and the spindle nut 16 accordingly runs back into the initial position.

[0018] By way of the pressure monitoring realized here it is ensured that the connection elements are pressed with the required pressure. This alone is not sufficient. Additionally although not shown here, the complete closure of the clamping pincer is also monitored. With regard to this the extensive patent literature already known is referred to. Such a monitoring may be effected by suitable sensors on the clamping pincer itself or a path monitoring may be effected. With the path monitoring in this case the displacement path of the roller advance element 15 may be monitored by way of suitable sensors. This sensor not shown here also conveys the corresponding information to the control 22, wherein any falling short of the required path leads to a corresponding error notification.

[0019] List of Reference Numerals

[0020]0 pressing tool

[0021]1 grip

[0022]2 function unit

[0023]3 receiver

[0024]4 clamping pincer

[0025]5 connection bolt

[0026]6 battery housing

[0027]7 display

[0028]8 trigger switch

[0029]9 light diodes

[0030]10 electric motor

[0031]11 reduction gear

[0032]12 drive pinion

[0033]13 shaft

[0034]14 threaded spindle

[0035]15 roller advance element

[0036]16 spindle nut

[0037]17 pressure flange

[0038]18 thrust bearing

[0039]19 radial bearing

[0040]20 housing plate

[0041]21 spindle housing

[0042]22 control

[0043]24 balls

[0044]25 force or pressure sensor

[0045]26 lever

[0046]27 thrust ring

[0047]28 counter-pressure ring

[0048]29 pin

[0049]30 rollers

[0050]31 axis pin 

1. An electrically operated pressing tool (0) with a spindle (14) for connecting tubular workpieces, with a fork-like receiver (3), with a clamping pincer (4) exchangeably held in this receiver by way of a connection bolt (5) and with a controlled electric drive motor (10) for actuating the clamping pincer, wherein there is present a spindle (14) which is driven by the electric drive motor (10) via a reduction gear (11) and which is in active connection with the clamping pincer (4), and wherein the spindle (14) is connected to the gear (11) via a shaft (13), wherein the shaft (13) passes through at least one radial bearing (19) and an axial thrust bearing (18) supported on the housing. (21) of the pressing tool, and wherein between the thrust bearing (18) and the support on the housing (20, 21) there is arranged a force or pressure sensor (25) which on reaching a predefined nominal value of the clamping force emits a switching signal (S) to the control (22) of the drive motor (10).
 2. A pressing tool according to claim 1, wherein the spindle (14) and the shaft (13) are connected flush to one another as one piece.
 3. A pressing tool according to claim 1, wherein the threaded spindle (14) is a screw spindle with a trapezoid thread and engages into an axially displaceably mounted spindle nut which acts on the clamping pincer (4) via a roller advance element (15).
 4. A pressing tool according to claim 2, wherein on the shaft (13) in the region close to the spindle there is integrally formed a pressure flange (17) and the shaft (13) passes through a housing plate (20), wherein between the pressure flange (17) and the housing plate (20) lies the thrust bearing (18) which on the one side is supported on the pressure flange (17) and on the other side via a force or pressure sensor (25) on the housing plate (20).
 5. A pressing tool according to claim 4, wherein the force or pressure, sensor (25) is a cylindrical element surrounding the shaft.
 6. A pressing tool according to claim 4, wherein the force or pressure sensor (25) is arranged between the housing plate (20) and a lever (26).
 7. A pressing tool according to claim 6, wherein the force or pressure sensor (25) is a piezoelectric sensor.
 8. A pressing tool according to claim 1, wherein the threaded spindle (14) is a circulating ball spindle.
 9. A pressing tool according to claim 1, wherein the force or pressure sensor (25) is a wire strain gauge. 